1. FIELD OF THE INVENTION
The invention relates to a method and apparatus for towing a pipeline, such as a gas transmission pipeline, by establishing sufficient buoyancy to raise the pipeline above the sea bed while maintaining it submerged within the body of water.
2. DESCRIPTION OF THE PRIOR ART
In offshore environments, such as the Gulf of Mexico, the North Sea, and in inland water bodies, such as rivers, canals and the like, there will be found submerged within the water extended lengths of tubing which is used to transmit chemicals, natural gas, produced hydrocarbons from offshore oil and gas wells, and other fluids from one location to another. Typically, such fluid transmission conduits, or pipelines, will be made up of a series of tubing sections which are threadably secured one to another and may be provided in lengths from a matter of 10 to 30 yards, up to a quarter mile in length, or more. When such tubing either breaks, or an abnormality or defect which adversely affects the integrity of the tubing occurs, it is necessary to move the tubing from the sea floor to a location for repair. In such instance, one or more towing vessels typically are used and are secured to the pipeline by means of a towing line. Of course, the drag on the vessel and the line caused by friction between the tubing and the floor of the sea causes considerable resistance and interference to the towing operation.
Sometimes gas pipeline transmission lines and the like are prepared in sections or lengths and such sections or lengths are towed to the position for offshore positioning on the sea bed floor. Again, the towing operation is greatly hampered if the tubing is required to be "dragged" along the sea bed floor.
Towing operations involving such tubing sections have incorporated the use of an inflatable-type sealing mechanism which is implaced within one end of the tubing to which is secured the tow line. The inflatable sealing element is inflated by air or other fluid and secures within the internal diameter of the towing end of the tubular conduit section. Still, such use of such inflatable sealing means has not been entirely satisfactory, because the tubing conduit continues to encounter considerable friction as a result of the drag upon it during the towing operation.
The present invention is an advancement in that it provides a means of towing such tubular conduits by eliminating the detrimental drag which previously resulted when the tubing section was dragged along the sea bed or other water channel floor. The present invention permits the tubing section which is towed to be placed into buoyancy such that there is no contact with the sea bed floor and, yet, the conduit still is maintained submerged within the water for ease of towing.